10c Noodling Stats

Instead of whingeing and complaining about all the coins I was missing from my circulating coin collection, I decided to go out and start looking for some of them.

Here are my statistics for the Australian 10c coin:



This is based on a sample size of 1912 coins, so I will likely add to it in the future. Here are some more graphs:





As you can see, a large number of pre-1997 coins have been removed from circulation, whereas most of the post-2006 coins still remain. The only exception to this is the 2011 coin, which seems to have been hoarded by collectors.

Much to my surprise, the 1991 and 1997 coins show up with roughly equal frequency, which contradicts the results of my last 19 years of noodling, where I found two or three 1991 10c coins but no 1997 ones. Now, I've found four of each within a single week, which equates to one in every 478 10c coins (or one in every $47.80' worth of 10c coins). However, I only found one 2011 coin, and no 1985 ones, so these are obviously much rarer than the 1991 and 1997 ones.

I've also noticed that since 2006, the 10c coins have oscillated between low-mintage and high-mintage years, with odd-numbered years having much lower mintages than even-number ones. This suggests that 2015 will be a low-mintage year, and if they fail to release more into circulation, the final mintage will probably end up around 7 million. This assumes that the mint has the correct mintage for the 2014 10c coin listed on their website, so if this is much higher than they say it is, then the mintage of the 2015 10c coin will also be higher, because that's what I'm basing my calculations on.

Finally, I have assumed that the mintage of the 1977 10c coin was 24.1 million, not the 10.9 million listed on the mint's website, because the latter figure looks erroneous when plotted on my graphs. I won't post the aberrant graphs here because they'll cause confusion, but in the second graph, the 1977 column rises to 1.37, and in the third graph, it rises to 38%. Such low attrition figures aren't met again until 2007, which is 30 years after these coins were released into circulation. This strongly suggests that the mint's figures are unreliable for this particular year, and that the actual mintage of the 1977 10c coin really was around 24 million.